Imaging apparatus having optical system and lens control unit for focus adjustment

ABSTRACT

An imaging apparatus comprises an optical system that includes a plurality of lens groups, each lens group including one or more lenses, at least one of the lens groups being independently movable with respect to the other lens groups and including a focus lens group for focusing the subject and a lens control unit that controls movement of the plurality of lens groups to bring into focus based on a feeding position of the focus lens group.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2010-277539 filed on Dec. 13, 2010 andNo. 2010-276339 filed on Dec. 10, 2010; the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an imaging apparatus for capturing asubject and generating image data of the subject and an optical systemused for the imaging apparatus.

BACKGROUND

Techniques are known for enabling macro photography for an imagingapparatus that captures a subject and generates electronic image data ofthe subject by inserting a relay optical system as an optical system.Such techniques are described in, for example, Japanese UnexaminedPatent Application Publication No. H11-183782.

SUMMARY

An imaging apparatus according to an aspect of the present invention forcapturing an image of a subject to generate electronic image datacomprises an optical system that includes a plurality of lens groups,each lens group including one or more lenses, at least one of the lensgroups being independently movable with respect to the other lens groupsand including a focus lens group for focusing the subject and a lenscontrol unit that controls movement of the plurality of lens groups tobring into focus based on a feeding position of the focus lens group.

The optical system according to an aspect of the present invention hasat least a first mode that focuses on a first close object from aninfinite object and a second mode that focuses on a third close objectfrom a second close object, the second close object being closer to theimaging apparatus than the infinite object, the third close object beingcloser to the imaging apparatus than the first close object. The opticalsystem comprises a focus lens group that is made up of one or two lensesand moves in an optical axis direction in focusing in each of the firstmode and the second mode and one or more mode change lens groups thatmove in the optical axis direction separately from the focus lens groupswhen the focusing is changed from the first mode to the second mode,wherein the following conditional expression (1) is satisfied:6<dB/dA<50  (1)where dA is a distance on the optical axis between an incoming plane andan outgoing plane of the focus lens group, and dB is a distance on theoptical axis between an incoming plane closest to an object side amongincoming planes of all lens groups that move when the focusing ischanged from the first mode to the second mode and an outgoing planeclosest to an image side among outgoing planes of the all lens groups,dB being a maximum distance if the distance is variable.

The above and other features, advantages and technical and industrialsignificance of this invention will be better understood by reading thefollowing detailed description of presently preferred embodiments of theinvention, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a configuration of a side facing aphotographer (rear side) of an imaging apparatus according to an aspectof the present invention.

FIG. 2 is a block diagram showing a configuration of the imagingapparatus.

FIG. 3 is a sectional diagram showing a configuration of a principalpart of a lens unit of the imaging apparatus.

FIG. 4 is a diagram showing principal components of the lens unit from asubject side.

FIG. 5A is a diagram showing a cross-sectional configuration of anoptical system of the lens unit in an infinite-distance focusing statewhen an optical system is set in a first mode.

FIG. 5B is a diagram showing a cross-sectional configuration of theoptical system in a short distance state when the optical system is setin the first mode.

FIG. 5C is a diagram showing a cross-sectional configuration of theoptical system in a longest-distance focusing state when the opticalsystem is set in a second mode.

FIG. 5D is a diagram showing a cross-sectional configuration of theoptical system in a short distance state when the optical system is setin the second mode.

FIG. 6 is a sectional view showing a retracted state of the opticalsystem.

FIG. 7 is a flow chart showing a process outline of the imagingapparatus.

FIG. 8 is a flow chart showing an outline of AF control operation of theimaging apparatus.

FIG. 9 is a graph showing relationship between inverse of a distancebetween the imaging apparatus and any subject and a feeding position ofthe lens unit.

FIG. 10 is a diagram showing a display example of a warning andschematically shows how the warning is displayed on the imagingapparatus.

FIG. 11 is a flow chart showing a process outline of mode switching ofthe imaging apparatus.

FIG. 12 is a flow chart showing a process outline of inner focustracking of the imaging apparatus according to the invention.

FIG. 13 is a flow chart showing a process outline of AF controloperation of the imaging apparatus according to a variation of thepresent invention.

FIG. 14 is a graph showing relationship between the inverse of adistance between the imaging apparatus according to the variation of thepresent invention and any subject and the feeding position of the lensunit.

FIG. 15 is a diagram showing a display sample indicating a warning andschematically shows how the warning is displayed on the imagingapparatus according to the variation of the present invention.

FIG. 16A is a diagram showing a cross-sectional configuration of theoptical systems of the lens unit in focusing on an object at a longdistance when the optical system is set in mode 3-1.

FIG. 16B is a diagram showing a cross-sectional configuration of theoptical system in a focusing state with a default state when the opticalsystem is set in mode 3-1.

FIG. 16C is a diagram showing a cross-sectional configuration of theoptical system in focusing on an object at a short distance when theoptical system is set in mode 3-1.

FIG. 17A is a diagram showing a cross-sectional configuration of theoptical system in focusing on an object at a long distance when theoptical system is set in mode 3-2.

FIG. 17B is a diagram showing a cross-sectional configuration of theoptical system in a focusing state with a default state when the opticalsystem is set in mode 3-2.

FIG. 17C is a diagram showing a cross-sectional configuration of theoptical system in focusing on an object at a short distance when theoptical system is set in mode 3-2.

FIG. 18A is a diagram showing a cross-sectional configuration of theoptical system in focusing on an object at a long distance when theoptical system is set in mode 3-3.

FIG. 18B shows a cross-sectional configuration of the optical system ina focusing state with a default state when the optical system is set inmode 3-3.

FIG. 18C is a diagram showing a cross-sectional configuration of theoptical system in focusing on an object at a short distance when theoptical system is set in mode 3-3.

FIG. 19 is a sectional view showing examples of states of the opticalsystem of another variation of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, preferred embodiments according to theinvention will be described below.

FIG. 1 is a perspective view showing a preferred configuration of a sidefacing a photographer of an imaging apparatus (rear side) according tothe invention. FIG. 2 is a block diagram showing a preferredconfiguration of the imaging apparatus. The imaging apparatus 1 shown inFIGS. 1 and 2 is a single-lens reflex digital camera provided with amain body 2 and a lens unit 3 that is detachably attached to the mainbody 2.

As shown in FIGS. 1 and 2, the main body 2 has an imaging unit 201, animaging drive unit 202, a signal processing unit 203, an operation inputunit 204, a display unit 205, a touch panel 206, a first communicationunit 207, a second communication unit 208, a flash unit 209, a timer210, a storage unit 211, a main control unit 212, a power source 213 anda power supply unit 214.

The imaging unit 201 has an image pickup device such as a CCD (ChargeCoupled Device) for receiving light collected by the lens unit 3 andconverting the light into electrical signals and a shutter.

The imaging drive unit 202 drives the image pickup device and theshutter based on a release signal.

The signal processing unit 203 performs signal processing such asamplification for an analogue signal output from the imaging unit 201and then performs A/D conversion to generate and output digital imagedata.

As shown in FIG. 1, the operation input unit 204 has a power switch 241,a release switch 242, a shooting mode switch 243, an operation switch244, a menu switch 245, a moving image switch 246 and a mode switch 247.

The power switch 241 turns the imaging apparatus 1 power on and off.

The release switch 242 inputs a still image signal to give aninstruction for still image shooting.

The shooting mode switch 243 gives an instruction for switching photoshooting modes set for the imaging apparatus 1.

The operation switch 244 inputs an instruction signal that givesinstruction to select or determine a setting of the imaging apparatus 1.The operation switch 244 has buttons 244 a, 244 b, 244 c and 244 d thatare up, down, left and right buttons, respectively, for selecting asetting in a menu screen and the like and a determination button 244 e(OK button) for determining operation using the buttons 244 a to 244 din the menu screen and the like. (See FIG. 1.)

The menu switch 245 inputs an instruction signal that gives aninstruction to display operation menu screen set for the imagingapparatus 1.

The moving image switch 246 inputs a moving image release signal to givean instruction for moving image shooting.

It is possible to switch modes arbitrarily using the mode switch 247between the first mode and the second mode for the optical system 301.Further, it is also possible to switch the modes manually while focusingthe optical system 301 automatically. Various examples of the modeswitching are given, for example, manual switching by a buttonoperation, a lever operation, a dial operation or an electric switch asdescribed above and auto switching by software process and the like. Forexample, when a photographer is performing macro-photography and asubject enters a range of a subject distance, automatic mode switchingis possible. In this case, when a focus lens is moving, it is alsopossible to perform focusing continuously during mode switching to thesecond mode. Further, it is also possible to perform focusing while anentire lens is retracting in a focusing operation from a second closeobject point to an infinite object point. The optical system 301includes both configurations where photographing ranges (object-imagedistances) of the first mode and that of the second mode overlap and donot overlap.

The display unit 205 is realized with a display panel made of liquidcrystal or organic EL (Electro Luminescence). The display unit 205displays the image data and information regarding operation of theimaging apparatus 1 and shooting, as needed.

The touch panel 206 is provided on a display screen of the display unit205. The touch panel 206 detects a contact position by the photographerbased on information displayed on the display unit 205 and receivesinput of an operation signal corresponding to the contact position. Fortouch panels, a resistor film system, an electrostatic capacitancesystem, an optical system and the like are generally known. However, anysystem for touch panels can be used without departing from theinvention.

The first communication unit 207 is a communication interface forcommunicating with the lens unit 3 attached to the main body 2. Thesecond communication unit 208 is a communication interface forcommunicating with an accessory unit 4 attached to the main body 2. Theaccessory unit 4 has an accessory communication unit 401 forcommunicating with the second communication unit 208 as a communicationinterface. Examples of the accessory unit 4 may include an electronicviewfinder (EVF), an electronic flash and the like.

The flash unit 209 is configured with a xenon lamp, an TED (LightEmitting Diode) and the like. The flash unit 209 flashes stroboscopiclight (auxiliary light) toward a viewing area to be captured by theimaging apparatus 1.

The storage unit 211 is realized with a semiconductor memory that isfixedly provided inside the imaging apparatus 1, such as a flash memoryor a DRAM (Dynamic Random Access Memory). The storage unit 211 storesthe image data, information regarding the lens unit 3 attachable to themain body 2, a zoom speed depending on a type of the lens unit 3 and thelike. Additionally, the storage unit 211 stores programs, parameters forexecuting the programs and the like. The storage unit 211 may include acomputer-readable recording medium such as an external memory card.

The main control unit 212 performs image processes such as edgeemphasis, color correction, γ correction for the image data, variouscomputational processing and operation control of the main body 2. Themain control unit 212 is realized with a CPU (Central Processing Unit)and the like.

The power source 213 is configured with a battery detachable from theimaging apparatus 1. The power supply unit 214 supplies electricity toeach component of the imaging apparatus 1, including the detachable lensunit 3. The power supply unit 214 may supply electricity from anexternal power source (not shown) to each component of the imagingapparatus 1.

The main body 2 having the above-described configuration may have anaudio input/output function, a communication function for communicationvia the Internet and the like.

The lens unit 3 comprises an optical system 301, a position detectingunit 302, a lens driving unit 303, a diaphragm driving unit 304, a lensoperation unit 305, a lens communication unit 306, a lens storage unit307 and a lens control unit 308.

The optical system 301 has a first lens group G1 having a positiverefracting power, a second lens group G2 having a positive refractingpower and a third lens group G3 having a positive refracting power. Thesecond lens group G2 is a focus lens group for focusing on a subject,which is an inner focus lens. The first lens group G1 and the third lensgroup G3 are mode change lens groups that move separately from the focuslens group along the optical axis when lens mode is switched.

The position detecting unit 302 detects a lens position in the opticalsystem 301 in the optical axis direction.

The lens driving unit 303 drives the lens in the optical system 301.

The diaphragm driving unit 304 drives a diaphragm in the optical system301. The lens operation unit 305 generates a signal for operating thelens in the optical system 301 and then inputs the generated operationsignal into the lens control unit 308. The lens operation unit 305 is aring-shaped push switch, for example.

The lens communication unit 306 communicates with the firstcommunication unit 207 in the main body 2 when attached to the main body2.

The lens storage unit 307 stores control programs and parameters todetermine a position and movement of the lens based on the instructionfrom the main control unit 212. The lens storage unit 307 storesinformation as a parameter to determine whether the inner focus lensreaches a limit region for focusing. Here, the limit region is decidedby a mechanical limit of a feeding position, a feeding control accuracyof the inner focus lens and the like. The mechanical limit of thefeeding position is defined by the region along the optical axis inwhich the driving unit 303 can drive the focus lens. When the mode isswitched between a mode that moves the lens groups other than the innerfocus lens and another mode that moves the entire optical systemincluding the inner focus lens, it is possible to set the limit regionarbitrarily within a range where object-image distances in the two modesoverlap. The lens storage unit 307 stores information regarding the modeswitching of the above-described two modes.

The lens control unit 308 controls operation of the lens unit 3 based onthe operation signal from the lens operation unit 305 and theinstruction signal from the main body 2. Specifically, the lens controlunit 308 drives the lens driving unit 303 to bring into focus and changezoom of the lens unit 3 based on the operation signal from the lensoperation unit 305 and drives the diaphragm driving unit 304 to changediaphragm values. Further, the lens control unit 308 determines whetherthe inner focus lens reaches the limit region for focusing. When thelens unit 3 is attached to the main body 2, the lens control unit 308may transmit information to the main body 2 on focus position and focaldistance of the lens unit 3, unique information to identify the lensunit 3 and the like. Such a lens control unit 308 is configured by a CPUand the like. The lens control unit 308 communicates with the maincontrol unit 212 on a lens state of the lens unit 3 at a predeterminedperiod. For this communication, a determination is made about whetherthe inner focus lens reaches the limit region for focusing, and theresult of this determination and information regarding a mode selectedfrom the above-described two modes are transmitted from the lens controlunit 308 to the main control unit 212.

The optical system 301 will be described in detail below. Generally, afocus lens group is made up of one or two lenses. It is more preferredthat the focus lens group be made up of two lenses including a negativelens and a positive lens. The focus lens group may be a single lens or acemented lens. Further, in focusing operation in the first mode and thesecond mode of the optical system 301, the focus lens group moves in theoptical axis direction. It is preferred that the focus lens group bemade up of only one lens group and that the focus lens group be only onelens group that moves in the optical axis direction in focusingoperation in the first mode and the second mode.

A configuration where the focus lens group is made up of one or twolenses and where the weight of the focus lens group is reducedadvantageously contributes to increase focus speed, save powerconsumption and achieve silence noise during photographing.Particularly, a configuration where the focus lens group is made up oftwo lenses including a negative lens and a positive lens advantageouslycontributes to achieve size reduction and aberration correctionsimultaneously. Such a configuration permits optical performancerequired for the focus lens group at a longer focusing distance positionand at a closer focusing distance position to be optimally achieved. Forshort distance photographing, focusing is changed from the first mode tothe second mode by moving the mode change lens group to an object side.This also advantageously contributes to increase focus speed, save powerconsumption and achieve silence noise during photographing in a shortdistance photographing range, i.e. the second mode.

Preferably, the first lens group G1, the second lens group G2 and thethird lens group G3 have a positive refracting power, respectively. Whenthe focusing is changed from the first mode to the second mode, thefirst lens group G1, the second lens group G2 and the third lens groupG3 move so that a distance between the first lens group and the thirdlens group is increased. This facilitates correction of sphericalaberration, curvature of field and the like in the second mode.

It is preferred that one of the one or more mode change lens groups bepositioned immediately before the focus lens group with respect to thesubject side, and a range of movement of the focus lens group in theoptical axis direction in the second mode be shifted to be closer to thesubject side than in the first mode. Accordingly, the distance betweenthe mode change lens group and the focus lens group for the first modeand the second mode can be configured in a manner not to be separatedtoo far from each other. As a result, for a mechanism where a lensbarrel holding the entire optical system is extended, for example, sizereduction of the optical system when not in use is achieved.

Further, it is preferred that the lens group disposed closest to thesubject side of the plurality of the lens groups constituting theoptical system 301 be one of the one or more mode change lens groups.That advantageously contributes to shorten an overall length of theoptical system 301 in the first mode and facilitates to make the lengthof the optical system 301 compact.

Further, it is preferred that both the mode change lens group and thefocus lens group move toward the subject side when the focusing ischanged from the first mode to the second mode. An off-axial light beamof the focus lens group can be configured in a manner to not be high bymoving the focus lens group toward the object side in mode changing.This permits a reduction in a diameter of the focus lens group Referringto FIG. 2, the first lens group G1 (first mode change lens group) andthe third lens group G3 (second mode change lens group) are provided asa mode change lens group. The plurality of the mode change lens groupscontributes to achieve optical performance in the first mode and thesecond mode.

Further, a relative distance between the first lens group G1 and thethird lens group G3 changes when the focusing is changed from the firstmode to the second mode. Accordingly, this facilitates correction ofspherical aberration, curvature of field and the like when the focusingis changed to the second mode.

Further, the focus lens group (second lens group G2) is disposed betweenthe two mode change lens groups. Accordingly, this contributes to reducethe diameter and weight of the focus lens group and facilitates toincrease auto focus speed.

FIG. 3 is a sectional view showing the configuration of the principalpart in the lens unit 3. Referring to FIG. 3, a more detailedconfiguration of the lens unit will be described below. In FIG. 3, thesubject side is shown on a left side (hereinafter referred to as “frontside”), and a side to be attached to the main body 2 is shown on a rightside (hereinafter referred to as “rear side”). The first lens group G1is made up of a biconcave negative lens L11 and a biconvex positive lensL12. The second lens group G2 is made up of a biconcave negative lensL21 and a biconvex positive lens L22. The third lens group G3 is made upof a negative meniscus lens L31 facing the subject side, a cemented lensmade up of a biconcave negative lens L32 and a biconvex positive lensL33 and a biconvex positive lens L34.

The lens unit 3 is an interchangeable lens. A bayonet mount 3 a to beattached to the main body 2 is provided at a rear end of the lens unit3. The mount 3 a is fixed to a fixing frame 3 b with screws and thelike. An electrical signal terminal (not shown) is provided on the mount3 a. The electrical signal terminal is an interface to electricallyconnect to the main body 2.

The lens unit 3 has a first-group frame 10 for holding the first lensgroup G1, a second-group frame 20 for holding the second lens group G2and a third-group frame 30 for holding the third lens group G3 and adiaphragm mechanism.

FIG. 4 is a diagram where the principal components are viewed from thesubject side to describe a mechanism for driving the first-group frame10. Since driving mechanisms for each frame are configured in a samemanner, details of only the driving mechanism of the first-group frame10 will be described below. In the first-group frame 10, one end of ashaft-shaped first-group lead screw 11 with threads (a screw forshifting the first lens group G1) is fitted into a hole in a protrusionon an inner peripheral side of the fixing frame 3 b. Another end of thefirst-group lead screw 11 is fitted into a hole in a front fixing frame3 d fixed to the fixing frame 3 b. The first-group lead screw 11 is heldto be freely rotatable around an axis parallel to the optical axis. At arear end of the first-group lead screw 11, a first screw gear 12 islocked by caulking, pressing and the like.

A first-group motor 14 formed integrally with a plate-like first-groupmotor base 13 is fixed to another protrusion on the fixing frame 3 bwith screws and the like. A first-group motor gear 15 is fixed to oneend of a rotating shaft of the first-group motor 14 by press fitting andthe like, and the first-group screw gear 12 engages with the first-groupmotor gear 15. A first-group position detection blade 16 where aplurality of slits is radially disposed about the rotating shaft isfixed to another end of the rotating shaft of the first-group motor 14by press fitting and the like. A first-group position detector 17composed of a photo interrupter is provided so that the first-groupposition detector 17 passes thorough an outer peripheral part of thefirst-group detection blade 16. The first-group motor 14, thefirst-group motor gear 15 and the like constitute the lens driving unit303. The first-group position detection blade 16, the first-groupdetector 17 and the like constitute the position detecting unit 302.

A female screw screwing with the first-group lead screw 11 is formed ona protrusion on an outer peripheral side of the first-group frame 10. Atan opposite position to the first-group lead screw 11 and thefirst-group screw gear 12 across the optical axis, a first-group guideshaft 18 whose both ends are fixed to the protrusion on the innerperipheral side of the fixing frame 3 b is provided parallel to theoptical axis (See FIG. 4.).

The first-group guide shaft 18 is fitted into a long hole extending in aradial direction of the optical axis formed on the protrusion on theouter peripheral side of the first-group frame 10. The first-group guideshaft 18 is positioned and held on the fixing frame 3 b by screwing thefirst-group lead screw 11 through a female screw.

Next, operation of the first-group frame 10 will be described. As thefirst-group motor 14 is rotated, the first-group screw gear 12 engagingwith the first-group motor gear 15 rotates and then the first-group leadscrew 11 integrally formed with the first-group screw gear 12 rotates.Hence rotational force is exerted to the first-group frame 10 engagingwith the first-group lead screw 11 to rotate about the rotating shaft ofthe first-group lead screw 11. Since turn of the first-group frame 10 isstopped by the first-group guide shaft 18, the first-group frame 10moves in the optical axis direction by a screw pitch in accordance withone turn of the first-group lead screw 11. A member such as a spring isappropriately provided (not shown) to prevent backlash occurring at thefirst-group lead screw 1 and the first-group guide shaft 18 inaccordance with turn of the first-group lead screw 11. Accordingly, turnof the first-group motor 14 is properly transmitted to the first-groupframe 10. With the lens unit 3 having such a configuration, turn of themotor shaft is detected by the first-group position detection blade 16fixed to the other end of the motor shaft of the first-group motor 14and the first-group position detector 17, and thus a position of thefirst-group frame 10 is accurately detected.

Since driving operation of the second-group frame 20 and the third-groupframe 30 are basically the same as that of the first-group frame 10,overlapping descriptions are omitted. In FIG. 3, members related tooperation of the second-group frame 20 are given numbers with 21, 22,23, . . . , and members related to operation of the third-group frame 30are given numbers with 31, 32, 33, . . . . Last one digit of thesemembers corresponds to those of the members related to operation of thefirst-group frame 10 that has a same function.

A diaphragm 40 has a plurality of diaphragm blades 41, a diaphragm plate42, a diaphragm base 43 and a diaphragm cover 44. The diaphragm base 43and the diaphragm cover 44 hold the diaphragm plate 42 so that thediaphragm plate 42 can be freely rotatable around the optical axis. Amechanism composed of a cam and a pin is disposed between the pluralityof the diaphragm blades 41 (not shown). With such a mechanism, as thediaphragm plate 42 rotates, the plurality of the diaphragm blades 41simultaneously operate along the cam and a diaphragm is stopped down, inother word, an iris diaphragm is formed.

The diaphragm base 43 is provided with a diaphragm motor base 52 forholding a diaphragm motor 51. A motor shaft of the diaphragm motor 51 isprovided with a diaphragm motor gear 53, which engages with a wheeldisposed on a protrusion on an outer peripheral side of the diaphragmplate 42. As the diaphragm motor 51 rotates, the diaphragm plate 42rotates and a size of the iris diaphragm formed by the diaphragm blades41 can be changed. A diaphragm detection blade 54 where a plurality ofslits is radially disposed about the rotating shaft is fixed to anotherend of the rotating shaft of the diaphragm motor 51 by press fitting andthe like. A diaphragm position detector 55 composed of a photointerrupter is provided so that the diaphragm position detector 55passes thorough an outer peripheral part of a diaphragm detection blade54. The diaphragm motor 51, the diaphragm motor gear 53 and the likeconstitute the lens driving unit 304.

Next, an operation ring 60 will be described. The operation ring 60 isfitted into an outer peripheral part of the fixing frame to be freelyrotatable in the optical axis direction. A cylindrical scale 61 isprovided on an inner peripheral side of the operation ring 60. The scale61 is a magnetic scale where north and south poles are alternatelyarranged at equal pitches circumferentially in a band shape. Longerdirections of the band are the optical axis direction.

A position detecting unit 62 provided on an outer peripheral part of thefixing frame 3 b to be opposed to the scale 61 is, for example, a GMRelement (giant magnetoresistance element), and resistance of theposition detecting unit 62 changes in accordance with change in magneticfield of the scale 61, and then relative position change to the scale 61is output as change of a voltage signal. The motors are controlled basedon this electrical signal, and that enables controlling the framesmanually. Setting Manual Focus (MF) or Auto Focus (AF) is possible byoperating an operation input unit 204.

The above-described motors and the position detecting unit 62 areelectrically connected to a substrate 70 where a principal circuit ofthe photographing lens is provided via a flexible substrate. Thesubstrate 70 is provided with a CPU. The substrate 70 is electricallyconnected to the main camera body 2 to transmit and receive a signal.

For the above-described motors, a rotary electromagnetic motor, apiezoelectric motor using a piezoelectric body or a linear motor thatoperates directly in the optical axis direction can be used, forexample. Alternatively, a stepping motor can be used. The positiondetector is unnecessary for this case.

The position detection blades disposed at each group motor are detectedby the position detector composed of the photo interrupter to detect thepositions of the first-group frame 10, the second-group frame 20 and thethird-group frame 30. Alternatively, the positions of the first-groupframe 10, the second-group frame 20 and the third-group frame 30 may bedetected by a magnetic sensing system using GMR elements or hallelements. Further alternatively, the positions of the first-group frame10, the second-group frame 20 and the third-group frame 30 may bedetected by detecting a change in capacitance. Further alternatively,the positions of the first-group frame 10, the second-group frame 20 andthe third-group frame 30 may be detected by detecting movement of theframe directly. Various systems for detecting a position of theoperation 60 can be also adopted same as in detecting the position ofthe first-group frame 10, the second-group frame 20 and the third-groupframe 30.

A specific embodiment of the optical system 301 will be described below.FIGS. 5A to 5D are cross-sectional views showing examples of states ofthe optical system 301. FIG. 5A shows a cross-sectional configuration ofthe lens in an infinite-distance focusing state when the optical system301 is set in the first mode (hereinafter referred to as “mode 1”). FIG.5B shows a cross-sectional configuration of the lens in a short distancefocusing state, that is, a state of focusing on a first close object,when the optical system 301 is set in the mode 1. (In FIG. 3, the lensunit 3 at this state is shown.) FIG. 5C shows a cross-sectionalconfiguration of the lens in focusing on an object at a longest distancewhen the optical system 301 is set in the second mode (hereinafterreferred to as “mode 2”), that is, a state of focusing on a second closeobject. FIG. 5D shows a cross-sectional configuration of the lens in ashort distance focusing state when the optical system 301 is set in themode 2, that is, a state of focusing on a third close object. FIG. 6 isa sectional view showing a retracted state of the optical system 301.

In FIGS. 5A to 5D, a reference symbol C denotes a plate-like cover glassdisposed on a surface of the image pickup device included in the imagingunit 201. A reference symbol I denotes an image surface I formed by theoptical system 301. The cover glass C may be provided on its surfacewith a wavelength range-limiting multilayer film, or it may have alow-pass filter function. Further, the cover glass C may have a filterfunction to remove adhering dust by ultrasonic oscillation. Further, thecover glass C may be divided into a plurality of plate-like coverglasses for each function.

In the mode 1, the second lens group G2 moves toward the object side tofocus on the first close object from the infinite object. When thefocusing is switched from the mode 1 to the mode 2 (from FIG. 5B to FIG.5C), all lens groups move to the subject side and then the entire lenssystem protrudes.

In the mode 2, only the second lens group G2 moves toward the objectside to focus on the third close object that is closer to the imagingapparatus 1 than the first close object from the second close objectthat is closer to the imaging apparatus 1 than the infinite object (fromFIG. 5C to FIG. 5D). The lens storage unit 307 stores lens position datafor the mode 1 and the mode 2. In the imaging apparatus 1, when a modeis set and a focusing signal is input, the lens control unit 308 moveseach of the lens groups according to the mode setting. Then, the lenscontrol unit 308 reads out the lens position control program andparameter from the lens storage unit 307 for mode switching and performscontrolling.

Further, when the focusing is switched from the mode 1 to the mode 2,the lens control unit 308 performs controlling to protrude the entirelens system toward the object side so that the distance between thefirst lens group G1 and the third lens group G3 is increased. Thus,effect of floating helps to reduce aberration fluctuation.

It is more preferred that the following conditional expression (1) besatisfied in the optical system 301 having the above-describedconfiguration:6<dB/dA<50  (1)

where dA is a distance on the optical axis between an incoming plane andan outgoing plane of the focus lens group. dB is a distance on theoptical axis between an incoming plane closest to the object side amongincoming planes of all lens groups that move when the focusing ischanged from the mode 1 to the mode 2 and an outgoing plane closest tothe image side among outgoing planes of all lens groups. If the distanceis variable, dB is a maximum distance. In conditional expression (1), itis more preferred that the lower limit value be 7 and further morepreferably 7.5. Further, in conditional expression (1), it is morepreferred that the upper limit value be 40 and further more preferably30.

Conditional expression (1) specifies a preferred value of a ratio of anaxial thickness of the lens group that move for mode changing and thefocus lens group. The distance on the optical axis of the focus lensgroup is reduced so that the lower limit value of conditional expression(1) may not be exceeded. Accordingly, that advantageously contributes toincrease speed, save power consumption and the like for auto focusing.The length in the optical axis direction of the lens group that moves inthe mode changing is reduced so that the upper limit value ofconditional expression (1) may not be exceeded. Accordingly, a mechanismfor moving the lens group becomes smaller.

Further, it is more preferred that the second lens group G2 in theoptical system 301 as a focus lens group satisfy the followingconditional expressions (2) and (3):2<|fA/ΔA1|<35  (2)2<|fA/ΔA2|<35  (3)where ΔA1 is a range of movement of the focus lens group in the opticalaxis direction in the mode 1, ΔA2 is a range of movement of the focuslens group in the optical axis direction in the mode 2, and fA is afocal length of the focus lens group. In conditional expressions (2) or(3), it is more preferred that the lower limit value be 5 and furthermore preferably 10. In conditional expressions (2) or (3), it is morepreferred that the upper limit value be 30 and further more preferably26.

It is preferred that the range of movement of the focus lens group havea certain size for a wider focusable range in the mode 1 and the mode 2.The refracting power of the focus lens group is properly reduced so thatthe lower limit values of conditional expressions (2) and (3) may not beexceeded. Accordingly, that helps to reduce aberration fluctuationcaused by movement of the focus lens group and contributes to achievefocusing performance. It is preferred that the focusable range be set sothat the upper limit values of conditional expressions (2) and (3) maynot be exceeded in order to satisfy a user's needs for use.

Further, it is more preferred that the third lens group G3 in theoptical system 301 satisfy the following conditional expression (4):1<f3/f<5  (4)where f3 is a focal length of the third lens group, and f is a focallength of the optical system upon focusing on the infinite object in themode 1. In conditional expression (4), it is further more preferred thatthe lower limit value be 2 and the upper limit value be 4.

Conditional expression (4) specifies a preferred value of the refractingpower of the third lens group. The positive refracting power of thethird lens group is reduced so that the lower limit value of conditionalexpressions (4) may not be exceeded. Accordingly, that helps to reduceaberration such as curvature of field. The positive refracting power ofthe third lens group is achieved so that the upper limit value ofconditional expressions (4) may not be exceeded. Accordingly, it becomeseasier to shorten the total length of the optical system, which isadvantageous in achieving size reduction of the lens barrel.

Further, it is more preferred that the second lens group G2 in theoptical system 301 satisfy the following conditional expression (5):0.5<|fA/f|<10  (5)In conditional expression (5), it is more preferred that the lower limitvalue be 0.7 and further more preferably 1. Further, in conditionalexpression (5), it is more preferred that the upper limit value be 8 andfurther more preferably 6.

Conditional expression (5) specifies a preferred value of the refractingpower of the focus lens group. The refracting power is adjusted so thatthe lower limit value of conditional expressions (5) may not be exceededto prevent an excessive focusing sensitivity of the focus lens.Accordingly, focusing control becomes easier. The refracting power isadjusted so that the upper limit value of conditional expressions (5)may not be exceeded. Accordingly, the focusable range is widened as anincrease in an amount of movement for focusing is reduced, and thatleads to size reduction of the lens barrel.

Further, it is preferred that the following conditional expressions (6)be satisfied when the mode change lens group is made up of two lensgroups and the lens group closer to the object side is a first modechange lens group and the lens group closer to the image side is thesecond mode change lens group:0.00<|(D1G−D2G)/D1G|<1.00  (6)where D1G is a moving distance of the first mode change lens grouptoward the object side when the focusing is changed from the mode 1 tothe mode 2 and D2G is a moving distance of the second mode change lensgroup toward the object side when the focusing is changed from the mode1 to the mode 2. In conditional expression (6), it is more preferredthat the lower limit value be 0.001, further more preferably 0.0055,further more preferably 0.015 and the most preferably 0.10. Further, inconditional expression (6), it is more preferred that the upper limitvalue be 0.60, further more preferably 0.40 and further more preferably0.30.

The distance between the first mode change lens group and the secondmode change lens group is changed and both lens groups are moved towardthe object side so that the lower and upper limit values of conditionalexpression (6) may not be exceeded. Thus correction function foraberration caused by distance change is achieved. Accordingly, that isadvantageous in reducing aberration fluctuation in the mode 1 and themode 2. Further, it is preferred that photographing magnification infocusing on the third close object in the mode 2 be a maximumphotographing magnification of the optical system. That advantageouslycontributes to increase focus speed at a nearly maximum photographingmagnification, for example.

It is possible to combine conditional expressions (1), (2), (3), (4),(5) and (6) arbitrarily. It also is possible to restrict the upper orlower limit values further.

According to the optical system 301 having the above-describedconfiguration, a configuration is possible where the distances in thetwo modes (mode 1 and mode 2) between the mode change lens group made upof the first lens group G1 and the third lens group G3 and the focuslens group made up of the second lens group G2 are not too long.Accordingly, the optical system 301 is suitable to reduce a mechanismsize.

Further, according to the optical system 301, in switching between thetwo modes, ranges of the photographable object-image distance partiallyoverlap. Accordingly, it is possible to prevent hollow defect in theranges of the photographable object-image distance.

Further, according to the optical system 301, when the focusing ischanged from the mode 1 to the mode 2, both of the mode change lensgroups and the focus lens group move toward the object side.Accordingly, a configuration is possible where off-axial light beam ofthe focus lens group is not high. Further, the diameter of the focuslens groups is reduced and weight reduction of the focus lens group isachieved.

Further, according to the optical system 301, since the focus lens groupis disposed between the plurality of the mode change lens groups, a sizein the diameter and weight is reduced. A configuration is possible wherethickness of the optical system in the optical axis direction isreduced, and that advantageously contributes to achieve size reductionof the optical system. Further, according to the optical system 301,that advantageously contributes to increase focus speed and save powerconsumption for focusing in the mode 1 and the mode 2.

In FIG. 5, the object-image distance in focusing on the second closeobject is longer than that in focusing on the first close object.Further, the magnification (absolute value) in focusing on the secondclose object is smaller than that in focusing on the first close object.

State change from the first close object focusing state to the secondclose object focusing state is shown in FIG. 5. However, movements ofthe lens groups in the mode changing are not limited to this.

For example, the lens groups may be moved toward the object side while aposition of the second lens group G2 (focus lens group) is adjusted sothat magnification may stay constant during the mode changing operation.Alternatively, the second lens group G2 may be moved so that absolutevalues of the magnification may continuously increase during the modechanging operation.

Alternatively, when the focusing is changed from the mode 1 to the mode2, the first lens group and the second lens group may be moved towardthe object side so that the distance between the first lens group andthe second lens group may stay constant. Accordingly, focusing can becontinuously performed despite a closer distance state comparing to theclose distance state in the mode 1. Alternatively, when the opticalsystem is retracted, the first lens group and the second lens group maybe positioned nearer to the third lens group, and, the first lens group,the second lens group and the third lens group may be controlled to bemoved toward the image side so that the distance between the third lensgroup and the first lens group and the second lens group may stayconstant (FIG. 6).

In any of these cases, the position of the focus lens group in the modechanging is uniquely determined. Accordingly, that enables to determinethe magnification uniquely in the mode changing.

Numerical data for this embodiment will be shown below. In the followingdata, IH denotes an image height, F_(No) denotes an F number, ω denotesa half angle of field, r denotes radius of curvature of each lenssurface, d denotes a distance between lens surfaces, nd denotes arefractive index of each lens for a d-line, νd denotes an Abbe constantfor each lens. In the numerical data below, length is given in mm and anangle is given in degree (°). In the numerical data, the object distanceis set to be an infinite, however, the focus state is changed by movingthe lens groups.

The biconcave negative lens L11 that makes up the first lens group hasaspheric surfaces on both sides. Here let x denote an optical axisprovided that the direction of travel of light is positive, and y denotea direction orthogonal to the optical axis. Then, aspheric configurationis given by the following conditional expression (7):x=(y ² /r)/[1+{1−(K+1)(y ² /r)²}^(1/2) ]+A ₄ y ⁴ +A ₆ y ⁶ +A ₈ y ⁸ +A ₁₀y ¹⁰ +A ₁₂ y ¹²  (7)where r denotes a paraxial radius of curvature, K denotes a conicalcoefficient, A₄, A₆, A₈, A₁₀, A₁₂ are a fourth, sixth, eighth, tenth andtwelfth aspheric surface coefficients, respectively.

1-1. Surface Data

TABLE 1 Surface no. r d nd νd Object plane ∞ ∞  1* −28.416 1.00 1.5831359.38  2* 27.152 0.90  3 59.029 2.61 1.88300 40.76  4 −22.026 Variable 5 −83.975 1.00 1.84666 23.78  6 79.450 0.20  7 18.492 2.23 1.8830040.76  8 −589.840 Variable  9 ∞ Variable 10 (Stop) ∞ 1.00 11 1036.2101.00 1.72825 28.46 12 14.719 3.59 13 −13.597 1.00 1.84666 23.78 14149.004 3.37 1.81600 46.62 15 −14.745 0.30 16 63.836 2.78 1.90366 31.3217 −38.092 9.23 18 ∞ Variable 19 ∞ 4.08 1.51633 64.14 20 ∞ 1.30 Imageplane ∞ (Light receiving surface)

1-2. Aspherical Data

-   -   1st Surface:        -   K=−1.656,        -   A₄=−3.45569×10⁻⁵,        -   A₆=−1.81632×10⁻⁷,        -   A₈=1.42064×10⁻¹¹    -   2nd Surface:        -   K=−10.037,        -   A₄=8.25272×10⁻⁵,        -   A₆=−5.69998×10⁻⁷

1-3. Zoom Data

TABLE 2 Infinite Close Close Close distance object 1 object 2 object 3IH 11.15 11.15 11.15 11.15 Focal length 24.91 25.29 25.14 25.53 F_(no.)2.86 2.63 2.82 2.59 2ω (°) 50.20 44.84 46.35 41.36 d4 3.75 1.00 3.751.00 d8 1.00 3.75 1.00 3.75 d9 0.00 0.00 0.50 0.50 d18 9.63 9.63 12.0012.00

1-4. Lens Unit Focal Length

-   -   f1=58.60, f2=34.63, f3=63.39

Practical numerical values of the conditional expressions (1) to (6) inthis embodiment will be cited.

TABLE 3 Object-image distance Close object 1 251.8097913 Close object 2266.7908343 Close object 3 161.9904492 Magnification Close object 1−0.129870803 Close object 2 −0.12080338 Close object 3 −0.249995456dB/dA 7.511309098 |fA/ΔA1| 12.58517245 |fA/ΔA2| 12.58517245 |fA/f|1.390170081 |f3/f| 2.54441 |(D1G − D2G)/D1G| 0.174216

Next, operation of the imaging apparatus 1 having the above-describedconfiguration will be described. FIG. 7 is a flow chart showing theprocess outline of the imaging apparatus 1. In FIG. 7, a state when theimaging apparatus 1 is set in a photo shooting mode will be described(step S101: Yes). For this state, a live view image display on thedisplay unit 205 is executed by the main control unit 212 (step S102).Subsequently, the lens control unit 308 transmits lens state informationto the main control unit 212 (step S103). At step S103, information suchas mode of the inner focus lens and focusing of the optical system 301is transmitted from the lens control unit 308 to the main control unit212. The main control unit 212 is capable of determining which mode isset, where the lenses are disposed on focal positions and the like.

After that, when a lens operation is performed (step S104: Yes), thelens control unit 308 performs an entire control to move the entireoptical system 301 via the lens driving unit 303 (step S105). After theentire control, an icon to input AF return operation is displayed on ascreen of the display unit 205.

When a position corresponding to this icon on the touch panel 6 ispressed by a user to input an instruction of the AF return operation(step S106: Yes) and the optical system 301 is in an AF range (stepS107: Yes), the process of the imaging apparatus 1 proceeds to stepS109. On the other hand, when the instruction of the AF return operationis input at step S106 and the optical system 301 is not in the AF range(step S107: No), the lens control 308 controls the entire optical system301 (step S108).

At step S104, when the lens operation is not performed (step S104: No),the lens control unit 308 performs AF control. Details of the AF controlwill be described later.

After the lens control unit 308 performs the AF control, when therelease switch 242 is pressed to input a still-image release signal(step S110: Yes), the imaging apparatus 1 captures an image (step S111)and the acquired image is stored in the storage unit 211 (step S112).

On the other hand, when the still-image release signal is not input(step S110: No) and the moving image switch 246 is pressed to input amoving-image release signal (step S113: Yes), the lens control unit 308performs the same AF control as step S109 (step S114). After that, theimaging apparatus 1 captures an image (step S115). At step S113, whenthe moving-image release signal is not input (step S113: No), theprocess of the imaging apparatus 1 returns to step S101.

After step S115, when a signal to finish photo shooting is input (stepS116: Yes), the process of the imaging apparatus 1 proceeds to stepS112. On the other hand, after step S115, when the signal to finishphoto shooting is not input (step S116: No), the process of the imagingapparatus 1 returns to step S114.

After step S112, when the power switch 241 is pressed (step S117: Yes),the main control unit 212 performs control to turn off power source(step S118) and ends a series of processes.

After step S112, when the power switch 241 is not pressed (step S117:No) and the lens unit 3 has been interchanged to another lens 3(hereinafter referred to as “lens unit 3′” to distinguish from the lensunit 3) (step S119: Yes), the main control unit 212 obtains lens typeinformation from the lens unit 3′ newly attached (step S120). Afterthat, the process of the imaging apparatus 1 returns to step S101. Onthe other hand, when the power switch 241 is not pressed (step S117: No)and the lens unit 3 has not been interchanged to another lens 3 (stepS119: No), the process of the imaging apparatus 1 returns to step S101.

Next, at step S101, a state when the imaging apparatus 1 is not set inthe photo shooting mode will be described (step S101: No). For thisstate, when the imaging apparatus 1 is in a playback mode (step S121:Yes), the main control unit 212 displays a file list on the display unit205 (step S122).

After that, when a file to be enlarged is selected through the operationinput unit 204 or the touch panel 206 (step S123: Yes), the main controlunit 212 reproduces and displays the selected file on the display unit205 (step S124).

Subsequently, when another file is selected (step S125: Yes), theprocess of the imaging apparatus 1 returns to step S124. On the otherhand, when another file is not selected (step S125: No), the process ofthe imaging apparatus 1 proceeds to step S126.

At step S126, when an end instruction is input through the operationinput unit 204 or the touch panel 206 (step S126: Yes), the process ofthe imaging apparatus 1 proceeds to step S117. On the other hand, whenthe end instruction is not input (step S126: No), the process of theimaging apparatus 1 returns to step S122.

At step S123, when the file to be enlarged is not selected through theoperation input unit 204 or the touch panel 206 (step S123: No), theprocess of the imaging apparatus 1 proceeds to step S126.

At step S121, when the imaging apparatus 1 is not in the playback mode,the process of the imaging apparatus 1 returns to step S101.

FIG. 8 is a flow chart showing the outline of the AF control operationof the imaging apparatus 1 (steps S109 and S114 shown in FIG. 7). FIG. 9is a graph showing relationship between the inverse of the distancebetween the imaging apparatus 1 and any subject and the feeding positionof the lens unit 3 during the AF control operation. In FIG. 9, theabscissa 1/L represents the inverse of the distance L between theimaging apparatus 1 and the subject, and the ordinate D represents avalue obtained by converting the feeding position of the lens unit 3into a focusing distance. A curve 501 shown in FIG. 9 schematicallyshows an extended amount of the inner focus lens during the AF control.In the above-described optical system 301, the inner focus lens is thesecond lens group G2. A curve 502 shown in FIG. 9 schematically showsextension of the entire optical system 301 during the AF control.

In FIG. 8, when the lens control unit 308 determines that, based on thefeeding position of the inner focus lens, the inner focus lens reachesthe limit region for focusing (step S201: Yes), the lens control unit308 transmits information indicating that the inner focus lens reachesthe limit region for focusing to the main control unit 212. The maincontrol unit 212 displays a warning on the display unit 205 based on theinformation transmitted from the lens control unit 308 (step S202).

FIG. 10 shows a display example of a warning and schematically shows howthe warning is displayed. Specifically, in FIG. 10, a photographer 601viewing a live view image displayed on the display unit 205 has toucheda dog 602 on the display screen as a subject to be photographed anddecided the subject to be tracked. As shown in FIG. 10, when the innerfocus lens reaches the limit region for focusing, a warning displayscreen 251 consisted of a message of “FORCED TRACKING” and two icons I1and I2 displayed as “OK” and “CANCEL”, respectively is displayed on thedisplay unit 205. If the inner focus lens reaches the limit region forfocusing as just described, the inner focus lens is fixed once (See asector II in FIG. 9). It is noted that a sector I in FIG. 9 shows astate before the inner focus lens reaches the limit region for focusing.In the sector I, the inner focus lens is controlled by the lens controlunit 308 so that the inner focus lens may protrude gradually whilewobbling. Since the inner focus lens wobbles in such a manner, movingdirection of the inner focus lens can be judged instantly using contrastchange information at that time. As a result, focusing speed of theimaging apparatus 1 in photography can be increased. Especially inphotography of moving images, focusing of the imaging apparatus 1 can besmoothly performed. The main control unit 212 gives instruction forwobbling and focusing direction and movement. The lens control unit 308controls the lenses for wobbling and focusing control based on theinstruction received from the main control unit 212.

In a state shown in FIG. 10, when the icon I1 is selected and acontinuation AF instruction is input (step S203: Yes), the imagingapparatus 1 performs mode switching (step S204). The lens control unit208 transmits information regarding the switched mode to the maincontrol unit 212 via the lens communication unit 306 and the firstcommunication unit 207. FIG. 11 is a flow chart showing the processoutline of mode switching. In FIG. 11, when the inner focus lens ismovable (step S301: Yes), the lens control unit 308 moves the lensgroups of the entire optical system 301 including the inner focus lensto bring into focus (step S302). This process of step S302 is shown in asector III in FIG. 9.

Subsequently, when the mode switching is completed (step S303: Yes), theimaging apparatus 1 returns to the main routine of the AF control. Onthe other hand, when the mode switching is not completed (step S303:No), the process of the imaging apparatus 1 returns to step S301.

At step S301, when the inner focus lens is not movable (step S301: No),the lens control unit 308 moves the lens groups excepting the innerfocus lens (step S304). Subsequently, the process of the imagingapparatus 1 proceeds to step S303.

After the imaging apparatus 1 completes the mode switching at step S204,the imaging apparatus 1 performs tracking using the inner focus lens(inner focus tracking) (step S205). FIG. 12 is a flow chart showing theprocess outline of the inner focus tracking of the imaging apparatus 1.In FIG. 12, when a specific subject in the image is selected through theoperation input unit 204 or the touch panel 206 and thus a trackinginstruction is input (step S401: Yes), the lens control unit 308evaluates the image to be tracked (step S402). On the other hand, thetracking instruction is not input (step S401: No), the lens control unit308 evaluates an entire image for focusing the nearest subject (stepS403).

A sector IV in FIG. 9 shows a state when the imaging apparatus 1performs the AF control again. In this state, the inner focus lensjudges focal deviation while wobbling. When the subject comes closerwhile the inner focus lens is judging the focal deviation, the innerfocus lens protrudes following the movement of the subject.Specifically, in the sector IV, in the optical system 301, only thesecond lens group G2 moves, however, the first lens group G1 and thethird lens group G3 do not move. The main control unit 212 gives aninstruction for timing of wobbling. On the other hand, the lens controlunit 308 performs lens control during the wobbling according toparameters stored in the lens storage unit 307.

After steps S402 or S403, the main control unit 212 performs adetermination of the moving direction and an adjustment focusingcondition of the lens (step S404). The moving direction is determinedbased on wobbling operation. The lens control unit 308 instructs thewobbling based on the control signal received from the main control unit212 and performs the lens control according to the instructed movingdirection and amount.

When it is determined as a result of step S404 that the lens is in focus(step S405: Yes), the process of the main control unit 212 returns tothe AF control.

When it is determined as the result of step S404 that the lens is not infocus (step S405: No) and the inner focus lens is closer to the shortdistance (step S406: Yes), the lens control unit 308 shifts the innerfocus lens to be closer to the long distance (step S407). On the otherhand, when it is determined as the result of step S404 that the lens isnot in focus (step S405: No) and the inner focus lens is not closer tothe short distance (step S406: No), the lens control unit 308 shifts theinner focus lens to be closer to the short distance (step S408). Afterthe steps S407 or S408, the process of the imaging apparatus 1 returnsto the main routine. The processes of steps S402 through S408 arecontrolled by the main control unit 212 and the lens control unit 308together. Specifically, the main control unit 212 performs determinationand instruction, and the lens control unit 308 performs actual controlfor movement.

The sector IV in FIG. 9 shows a state when the imaging apparatus 1performs the AF control again. In this state, the inner focus lensprotrudes while wobbling and the entire optical system 301 is fixed.That is, in the sector IV, only the second lens group G2 moves, however,the first lens group G1 and the third lens group G3 do not move.

Referring again to FIG. 8, the process of the AF control will bedescribed. At step S203, when the AF continuation instruction is notinput (step S203: No), the imaging apparatus 1 stops tracking (stepS206). Subsequently, the process of the imaging apparatus 1 proceeds tostep S207.

At step S207, when an instruction signal to finish the control is input(step S207: Yes), the process of the imaging apparatus 1 returns to themain routine of the AF control. On the other hand, at step S207, whenthe instruction signal to finish the control is not input (step S207:No), the process of the imaging apparatus 1 returns to step S201.

At step S201, when the inner focus lens does not reach the limit regionfor focusing (step S201: No), the imaging apparatus 1 performs the innerfocus tracking (step S208). The process of the inner focus tracking isthe same as step S205.

According to the imaging apparatus described above, it is possible tochange protrusion and retraction of the optical system naturally nearthe limit region of the focus lens group. Accordingly, control dependingon characteristics of the optical system and photo shooting conditionsis possible.

Further, the imaging apparatus described above advantageouslycontributes to reducing driving sound (silence noise), increasing autofocus speed, and is advantageous in silence noise even in a shortdistance range.

Further, the imaging apparatus described above enables the most suitablefocusing for the subject in macro mode and by a user's AF operation. Inaddition, the imaging apparatus enables control that follows operationsnaturally and quickly with an energy-saving effect.

Further, a camera with the compact optical system described above iseasy to carry. Furthermore, a subject in a short distance is supportedsince quick and silent focusing for moving images is a priority.

FIG. 13 is a flow chart showing the process outline of AF control of animaging apparatus according to a variation of the present invention. Theconfiguration of the imaging apparatus according to the variation is thesame as the imaging apparatus 1 described above. FIG. 14 is a graphshowing relationship between the inverse of the distance between theimaging apparatus 1 and any subject and the feeding position of the lensunit. In FIG. 14, the abscissa 1/L represents the inverse of thedistance L between the imaging apparatus 1 and the subject, and theordinate D axis represents a value obtained by converting the feedingposition of the lens unit 3 into a focusing distance. A curve 701 shownin FIG. 14 schematically shows an extended amount of the inner focuslens (the second lens group G2) during the AF control. A curve 702 shownin FIG. 14 schematically shows extension of the entire optical system301 during the AF control.

In FIG. 13, when the lens control unit 308 determines that, based on thefeeding position of the inner focus lens, the inner focus lens reachesthe limit region for focusing (step S501: Yes), the lens control unit308 transmits information indicating that the inner focus lens reachesthe limit region for focusing to the main control unit 212. The maincontrol unit 212 displays a warning on the display unit 205 based on theinformation transmitted from the lens control unit 308 (step S502). FIG.15 shows a display example of a warning and schematically shows how thewarning is displayed on the imaging apparatus according to thevariation. Specifically, in FIG. 15, the photographer 601 viewing a liveview image displayed on the display unit 205 has touched the dog 602 onthe display screen as a subject to be photographed and decided thesubject to be tracked. As shown in FIG. 15, when the inner focus lensreaches the limit region for focusing, a warning display screen 252consists of a message of “PREDICTIVE TRACKING” and two icons 13 and 14displayed as “OK” and “CANCEL”, respectively is displayed on the displayunit 205. Thus, if the inner focus lens reaches the limit region forfocusing, the position of the inner focus lens is fixed once (a sectorII in FIG. 14). It is noted that a sector I in FIG. 14 shows a statebefore the inner focus lens reaches the limit region for focusing as thesame as shown in FIG. 9.

In a state shown in FIG. 15, when the icon 13 is selected and acontinuation AF instruction is input (step S503: Yes), the main controlunit 212 performs tracking prediction (step S504). In the trackingprediction, a motion vector at a representative point of a subject isused, for example, to calculate a movement velocity of the subject, anda movement distance AD after elapse of a predetermined time is acquired.Accordingly, in this variation, the main control unit 212 has a functionas a prediction calculating unit for predicting position change of thesubject.

After step S504, the imaging apparatus 1 performs mode switching basedon the tracking prediction result (step S505). This mode switching isthe same as the above-described embodiment except that the movementdistance of the optical system 301 is determined based on the predictionresult (See FIG. 11.). The mode switching is shown in a sector III inFIG. 14.

Subsequently, the imaging apparatus 1 performs inner focus tracking(step S506). A sector IV in FIG. 14 shows a state when the imagingapparatus 1 performs the AF control again. In this state, the lenscontrol unit 308 instructs the inner focus lens to wobble, and when thesubject comes closer while the main control unit 212 is judging focaldeviation, the inner focus lens protrudes following the subject. In thisinstance, in the sector IV, only the second lens group G2 moves,however, the first lens group G1 and the third lens group G3 do notmove.

Steps S506 to S509 sequentially correspond to steps S205 to S208 in FIG.8. The process of the inner focus tracking at step S509 is the same asstep S506 described above.

As the same as the embodiment of the invention described above,according to the variation of the invention described above, the controldepending on characteristics of the optical system and photo shootingconditions is possible.

Variation of the Optical System

Next, a variation of the optical system included in the imagingapparatus will be described. In this variation, a lens configuration ofthe optical system is the same as that of the above-describedembodiment. In this variation, the optical system 301 has a third mode 1(hereinafter referred to as “mode 3-1”), a third mode 2 (hereinafterreferred to as “mode 3-2”) and a third mode 3 (hereinafter referred toas “mode 3-3”) to add to the mode 1 and the mode 2. When an object-imagedistance at the shortest distance in the mode 2 (“Close object 3” in thenumerical data) denotes L, the distance in the mode 3-1 (firstvariation) is 4L, the distance in the mode 3-2 (second variation) is 2Land the distance in the mode 3-3 (third variation) is 4L/3.

When the focusing is changed from the mode 1 to the mode 3-1, the secondlens group G2 moves toward a default position to be uniquely determined.Similarly, in the mode 3-2 and the mode 3-3, the second lens group G2moves toward default positions, respectively, which are determineddepending on each entire feeding position for the inner focus lensgroup. When a lens system is designed, data for the entire feedingpositions is determined and is stored in the lens storage unit 307 in atable format as a parameter.

In the mode 2, the default position is at the shortest object point(Close object 3). When the focusing is changed from the mode 1 to themode 2, the position of the focus lens group sequentially shifts inorder of from the infinite object point of the mode 1, the defaultposition of the mode 3-1, the default position of the mode 3-2, thedefault position of the mode 3-3 and to the shortest object point of themode 2.

The above-described focus position determination during the modechanging enables specific magnification depending on the entireextension operation. Accordingly, magnification setting with a scale andthe like is performed, and that is advantageous for manual focusingoperation. Further, when focusing is performed by auto-focus in eachmode, the second lens group as the focus lens group is moved and fastfocusing in each mode state is possible. It is preferred that the userbe appropriately allowed to set extension of entire optical system ormovement of only the focus lens group in order to focus on the shortdistance.

FIGS. 16A to 16C are sectional views showing examples of states of themode 3-1. Specifically, FIG. 16A shows a cross-sectional configurationof the lens in focusing on an object at a long distance in the mode 3-1.FIG. 16B shows a cross-sectional configuration of the lens in a focusingstate with a default state in the mode 3-1. FIG. 16C shows across-sectional configuration of the lens in focusing on an object at ashort distance in the mode 3-1. In the mode 3-1, the second lens groupmoves toward a subject side to focus on the subject. (from FIG. 16B toFIG. 16C)

FIGS. 17A to 17C are the sectional views showing examples of states ofthe mode 3-2. Specifically, FIG. 17A shows a cross-sectionalconfiguration of the lens in focusing on an object at a long distance ofmode 3-2. FIG. 17B shows a cross-sectional configuration of the lens ina focusing state with a default state in mode 3-2. FIG. 17C shows across-sectional configuration of the lens in focusing on an object at ashort distance in mode 3-2. The focusing is performed the same as in themode 3-1.

FIGS. 18A to 18C are the sectional views showing examples of states ofthe mode 3-3. Specifically, FIG. 18A shows the cross-sectionalconfiguration of the lens in focusing on an object at a long distance inmode 3-3. FIG. 18B shows the cross-sectional configuration of the lensin a focusing state with a default state in mode 3-3. FIG. 18C shows thecross-sectional configuration of the lens in focusing on an object at ashort distance in mode 3-3. The focusing is performed the same as in themode 3-1.

Numerical data for the variation will be shown below.

Mode 3-1:

TABLE 4 Long distance Default Short distance IH 11.15 11.15 11.15 Focallength 24.97 25.00 25.35 F_(no.) 2.86 2.86 2.86 2ω (°) 49.20 48.71 43.94d4 3.75 3.49 1.00 d8 1.00 1.26 3.75 d9 0.13 0.13 0.13 d18 10.22 10.2210.22

Mode 3-2:

TABLE 5 Long distance Default Short distance IH 11.15 11.15 11.15 Focallength 25.03 25.12 25.41 F_(no.) 2.86 2.86 2.86 2ω (°) 48.23 46.87 43.06d4 3.75 3.02 1.00 d8 1.00 1.73 3.75 d9 0.25 0.25 0.25 d18 10.82 10.8210.82

Mode 3-3:

TABLE 6 Long distance Default Short distance IH 11.15 11.15 11.15 Focallength 25.08 25.29 25.47 F_(no.) 2.86 2.86 2.86 2ω (°) 47.28 44.52 42.20d4 3.75 2.24 1.00 d8 1.00 2.51 3.75 d9 0.38 0.38 0.38 d18 11.41 11.4111.41

Object-image distances and magnifications for the variation will becited below.

Mode 3-1:

TABLE 7 Longest Default Shortest Object-image distance 216.1417987878.903759 647.9617966 Magnification −0.030363557 −0.042284666−0.160069243

Mode 3-2:

TABLE 8 Longest Default Shortest Object-image distance 470.1216975323.9808983 192.0973976 Magnification −0.060618361 −0.094304656−0.190155945

Mode 3-3:

TABLE 9 Longest Default Shortest Object-image distance 334.330522215.9872655 174.8724625 Magnification −0.090765389 −0.160701685−0.220131699

In this variation, it is also possible to switch the modes using themode switch 247 among the modes 1, 2, 3-1, 3-2 and 3-3.

A Second Variation of the Optical System

FIGS. 19A to 19D show configurations and operation outlines of anothervariation of the optical system (hereinafter referred to as “variation2”). As shown in FIGS. 19A to 19D, the optical system according to thisvariation comprises, in order from the front side, a first lens groupG11 having a positive refracting power with a diaphragm stop S and asecond lens group G12 having a negative refracting power.

The first lens group G11 is made up of a positive meniscus lens L41convexing to an object side, a negative meniscus lens L42 convexing tothe object side, a diaphragm stop S′, a cemented lens made up of abiconcave negative lens L43 and a biconvex positive lens L44 and abiconvex positive lens L45.

The second lens group G12 is made up of a negative meniscus lens L51convexing to the object side. Aspheric surfaces are used on both sidesof a biconvex positive lens L45 on the image surface I of the first lensgroup G11.

In the mode 1, the second lens group G12 moves toward the rear side (themain body 2 side) in focusing on a first close object from an infiniteobject (from FIG. 19A to FIG. 19B). When the focusing is switched fromthe mode 1 to the mode 2, all lens groups move to the object side andthen the optical system protrudes (from FIG. 19B to 19C).

In the mode 2, only the second lens group G2 moves toward the imagesurface I side in focusing on a third close object that is closer thanthe first close object from the second close object that is closer thanthe infinite object (from FIG. 19C to FIG. 19D).

It is noted that a moving system of the second lens group in modechanging may be optional as long as the second lens group is movable.

Accordingly, a lens group where the focusing lens group is positionedclosest to the image in the optical system helps to reduce sphericalaberration fluctuation by focusing.

Numerical data for variation 2 will be shown below.

2-1. Surface data

TABLE 10 Surface no. r d nd νd Object plane ∞ ∞  1 20.357 3.10 1.8830040.76  2 56.116 0.10  3 14.804 0.95 1.71300 53.87  4 7.197 7.87  5 ∞0.45  6 (Stop) ∞ 1.15  7 ∞ 3.99  8 −16.892 0.83 1.69895 30.13  9 19.6693.86 1.77250 49.60 10 −23.985 0.10 11* 33.830 4.20 1.58313 59.38 12*−12.588 Variable 13 36.891 2.00 1.51633 64.14 14 14.627 Variable 15 ∞Variable 16 ∞ 2.21 1.51633 64.14 17 ∞ 3.42 Image surface ∞ (Image pickupsurface)

2-2. Aspherical Data

-   -   11th Surface:        -   K=0.000,        -   A₄=−4.49818×10⁻⁵,        -   A₆=1.02178×10⁻⁹    -   12th Surface:        -   K=−0.935,        -   A₄=2.10096×10⁻⁵    -   A₆=−1.60991×10⁻⁷

2-3. Zoom Data

TABLE 11 Infinite Close Close Close distance object 1 object 2 object 3IH 11.15 11.15 11.15 11.15 Focal length 25.00 21.81 25.00 21.81 F_(no.)2.86 2.53 2.86 2.53 2ω (°) 46.41 47.06 42.05 42.32 d12 0.10 4.68 0.104.68 d14 13.05 8.47 13.05 8.47 d15 9.63 9.63 15.52 15.52

2-4. Lens Unit Focal Length

-   -   f1=16.13, f2=−48.42

It is more preferred that the conditional expressions (1) to (6) besatisfied in variation 2.

TABLE 12 Object-image distance Close object 1 151.8574881 Close object 2170.1538021 Close object 3 106.5408394 Magnification Close object 1−0.23 Close object 2 −0.235509551 Close object 3 −0.50 dB/dA 14.3547705|fA/ΔA1| 10.58649013 |fA/ΔA2| 10.58649013 |fA/f| 1.936613381 f3/f —|(D1G − D2G)/D1G| —

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot so limited to the specific details and representative embodimentsshown and described herein. Accordingly, various modifications may bemade without departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An imaging apparatus for capturing an image of asubject to generate electronic image data, comprising: an optical systemthat includes a plurality of lens groups, each lens group including oneor more lenses, at least one of the lens groups being independentlymovable with respect to the other lens groups, and at least one of thelens groups being a focus lens group for focusing the subject; and alens control unit that controls movement of the plurality of lens groupsto bring the subject into focus based on a feeding position of the focuslens group within a focus region, wherein the optical system has a firstmode and a second mode, and the plurality of lens groups includes one ormore mode change lens groups that move in an optical axis direction whenthe focusing is changed from the first mode to the second mode.
 2. Theimaging apparatus according to claim 1, wherein the lens control unitmoves at least one of the plurality of lens groups to bring the subjectinto focus when the focus lens group reaches a limit region forfocusing.
 3. The imaging apparatus according to claim 2, wherein the atleast one of the plurality of lens groups brought into focus on thesubject includes the focus lens group, and the lens control unit movesthe focus lens group in a different way from the other lens groups. 4.The imaging apparatus according to claim 3, wherein a mode that movesthe lens groups other than the focus lens group and a mode that movesthe entire optical system including the focus lens group are selectivelyset.
 5. The imaging apparatus according to claim 4, further comprising amain control unit that communicates with the lens control unit andcontrols a main body of the imaging apparatus, wherein the lens controlunit transmits to the main control unit information indicating aselected one of the mode that moves the lens groups other than the focuslens group and the mode that moves the entire optical system includingthe focus lens group.
 6. The imaging apparatus according to claim 5,wherein the main control unit transmits to the lens control unit asignal for instructing the lens control unit to switch between the modethat moves the lens groups other than the focus lens group and the modethat moves the entire optical system including the focus lens group. 7.The imaging apparatus according to claim 6, further comprising an inputunit that receives a mode switching instruction signal, wherein the maincontrol unit transmits to the lens control unit the signal forinstructing the lens control unit to switch between the modes based onthe mode switching instruction signal input through the input unit. 8.The imaging apparatus according to claim 1, further comprising: adisplay unit that displays an image corresponding to the image data; andan input unit that receives a signal for specifying a subject to befocused in the image displayed by the display unit, wherein the lenscontrol unit brings the subject specified by the signal received by theinput unit into focus.
 9. The imaging apparatus according to claim 8,further comprising a prediction computing unit that performs calculationfor predicting a change in position of the subject specified by theinput unit.
 10. The imaging apparatus according to claim 1, furthercomprising a display unit that displays an image corresponding to theimage data, wherein the display unit displays a warning when the focuslens group reaches a limit region for focusing.
 11. The imagingapparatus according to claim 10, further comprising an input unit thatreceives an instruction signal, wherein the lens control unit moves atleast one of the plurality of lens groups to bring the subject intofocus based on the instruction signal received by the input unit whilethe warning is displayed.
 12. The imaging apparatus according to claim1, further comprising a lens unit that is detachably connected to a mainbody of the imaging apparatus, the lens unit including the opticalsystem and the lens control unit.
 13. The imaging apparatus according toclaim 12, further comprising a main control unit that communicates withthe lens control unit and controls a main body of the imaging apparatus,wherein the lens control unit determines whether the focus lens groupreaches a limit region for focusing and transmits a result of thedetermination to the main control unit, and the main control unittransmits a control signal for the plurality of lens groups to the lenscontrol unit based on the result of determination received from the lenscontrol unit.
 14. The imaging apparatus according to claim 1, whereinthe first mode is a mode that focuses on a first close object from aninfinite object, the second mode is a mode that focuses on a secondclose object from a third close object, the second close object beingcloser to the imaging apparatus than the first close object, the thirdclose object being closer to the imaging apparatus than the infiniteobject, the focus lens group is made up of at least one lens and movesin the optical axis direction when focusing in each of the first modeand the second mode, and the one or more mode change lens groups move inthe optical axis direction separately from the focus lens groups whenthe focusing is changed from the first mode to the second mode.
 15. Theimaging apparatus according to claim 14, wherein the optical systemincludes a first lens group, a second lens group, and a third lens groupthat are arranged in order from a subject side to an image side, thefirst lens group and the third lens group are the mode change lensgroups, the second lens group is the focus lens group, and the first,second, and third lens groups move to the subject side with respect toan image surface when the focusing is changed from the first mode to thesecond mode.
 16. The imaging apparatus according to claim 1, wherein thelens control unit performs wobbling in an optical axis direction on thefocus lens group while moving the focus lens group to focus.
 17. Theimaging apparatus according to claim 1, wherein the focus lens groupmoves in the optical axis direction when focusing in each of the firstmode and the second mode.
 18. The imaging apparatus according to claim1, wherein the focus lens group is different from the one or more modechange lens groups.
 19. The imaging apparatus according to claim 1,wherein the first mode is a mode that focuses on a first close objectfrom an infinite object, and the second mode is a mode that focuses on asecond close object from a third close object, the second close objectbeing closer to the imaging apparatus than the first close object, thethird close object being closer to the imaging apparatus than theinfinite object.
 20. An imaging apparatus for capturing an image of asubject to generate electronic image, data, comprising: an opticalsystem that includes a plurality of lens groups, each lens groupincluding one or more lenses, at least one of the lens groups beingindependently movable with respect to the other lens groups, and atleast one of the lens groups being a focus lens group for focusing thesubject; and a lens control unit that controls movement of the pluralityof lens groups to bring the subject into focus based on a feedingposition of the focus lens group within a focus region, wherein a modethat moves the lens groups other than the focus lens group and a modethat moves the entire optical system including the focus lens group areselectively set.
 21. The imaging apparatus according to claim 20,further comprising a main control unit that communicates with the lenscontrol unit and controls a main body of the imaging apparatus, whereinthe lens control unit transmits to the main control unit informationindicating a selected one of the mode that moves the lens groups otherthan the focus lens group and the mode that moves the entire opticalsystem including the focus lens group.
 22. The imaging apparatusaccording to claim 21, wherein the main control unit transmits to thelens control unit a signal for instructing the lens control unit toswitch between the mode that moves the lens groups other than the focuslens group and the mode that moves the entire optical system includingthe focus lens group.
 23. The imaging apparatus according to claim 22,further comprising an input unit that receives a mode switchinginstruction signal, wherein the main control unit transmits to the lenscontrol unit the signal for instructing the lens control unit to switchbetween the modes based on the mode switching instruction signal inputthrough the input unit.
 24. The imaging apparatus according to claim 20,further comprising: a lens unit that is detachably connected to a mainbody of the imaging apparatus, the lens unit including the opticalsystem and the lens control unit; and a main control unit thatcommunicates with the lens control unit and controls a main body of theimaging apparatus, wherein the lens control unit determines whether thefocus lens group reaches a limit region for focusing and transmits aresult of the determination to the main control unit, and the maincontrol unit transmits a control signal for the plurality of lens groupsto the lens control unit based on the result of determination receivedfrom the lens control unit.
 25. An imaging apparatus for capturing animage of a subject to generate electronic image data, comprising: anoptical system that includes a plurality of lens groups, each lens groupincluding one or more lenses, at least one of the lens groups beingindependently movable with respect to the other lens groups, and atleast one of the lens groups being a focus lens group for focusing thesubject; a lens control unit that controls movement of the plurality oflens groups to bring the subject into focus based on a feeding positionof the focus lens group within a focus region; a display unit thatdisplays an image corresponding to the image data, wherein the displayunit displays a warning when the focus lens group reaches a limit regionfor focusing; and an input unit that receives an instruction signal,wherein the lens control unit moves at least one of the plurality oflens groups to bring the subject into focus based on the instructionsignal received by the input unit while the warning is displayed. 26.The imaging apparatus according to the claim 25, further comprising amain control unit that communicates with the lens control unit andcontrols a main body of the imaging apparatus, wherein the lens controlunit transmits to the main control unit information indicating aselected one of a mode that moves the lens groups other than the focuslens group and a mode that moves the entire optical system including thefocus lens group.
 27. The imaging apparatus according to claim 26,wherein the main control unit transmits to the lens control unit asignal for instructing the lens control unit to switch between the modethat moves the lens groups other than the focus lens group and the modethat moves the entire optical system including the focus lens group. 28.The imaging apparatus according to claim 27, further comprising an inputunit that receives a mode switching instruction signal, wherein the maincontrol unit transmits to the lens control unit the signal forinstructing the lens control unit to switch between the modes based onthe mode switching instruction signal input through the input unit. 29.The imaging apparatus according to claim 25, further comprising: a lensunit that is detachably connected to a main body of the imagingapparatus, the lens unit including the optical system and the lenscontrol unit; and a main control unit that communicates with the lenscontrol unit and controls a main body of the imaging apparatus, whereinthe lens control unit determines whether the focus lens group reaches alimit region for focusing and transmits a result of the determination tothe main control unit, and the main control unit transmits a controlsignal for the plurality of lens groups to the lens control unit basedon the result of determination received from the lens control unit.